VMware Patches VM Escape Flaw Disclosed at Chinese Hacking Contest

VMware informed customers on Friday that patches are available for a critical virtual machine (VM) escape vulnerability disclosed recently by a researcher at the GeekPwn2018 hacking competition.

Organized by the security team of Chinese company Keen Cloud Tech, GeekPwn is a hacking competition that in the past years has led to the discovery of many important vulnerabilities. The competition has been held in China since 2014, but starting with 2017 there has also been an event in the United States.

GeekPwn2018 took place in Shanghai, China, on October 24-25, and its initial prize pool was $800,000.

One of the most interesting entries in the contest came from a researcher at China-based security firm Chaitin Tech, who discovered a guest-to-host escape vulnerability affecting several VMware products. He also identified a less severe information disclosure bug.

Shortly after the VM escape exploit was demonstrated, Chaitin Tech wrote on Twitter that it was the first time anybody managed to escape VMware ESXi and get a root shell on the host system. The company posted a short video showing the exploit in action.

VMware on Tuesday informed customers that it had been provided the details of the vulnerabilities and on Friday it published an advisory describing the flaws and available patches.

According to the virtualization giant, the vulnerabilities, tracked as CVE-2018-6981 and CVE-2018-6982, are caused by an uninitialized stack memory usage bug in the vmxnet3 virtual network adapter.

CVE-2018-6981 affects ESXi, Fusion and Workstation products, and it can allow a guest to execute arbitrary code on the host, while CVE-2018-6982, which only impacts ESXi, can result in an information leak from the host to the guest. VMware pointed out that the vulnerabilities are only present if the vmxnet3 adapter is enabled – other adapters are not impacted.

It’s worth noting that Chaitin Tech researchers have also earned significant prizes at ZDI’s Pwn2Own hacking competition in the past years. It’s unclear how much they earned for the VMware product vulnerabilities disclosed at GeekPwn.

Eduard Kovacs (@EduardKovacs) is a contributing editor at SecurityWeek. He worked as a high school IT teacher for two years before starting a career in journalism as Softpedia’s security news reporter. Eduard holds a bachelor’s degree in industrial informatics and a master’s degree in computer techniques applied in electrical engineering.